Internal Combustion Engines: The Worst Form of Vehicle Propulsion -

Except for All the Other FormsPaul D. Ronney

Deparment of Aerospace and Mechanical EngineeringUniversity of Southern California

USC Microseminar, August 17 – 18, 2017Download this presentation:

http://ronney.usc.edu/WhyICEngines.zip

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OutlineØ Introductions

Ø PersonalØ To this subject

Ø Some remarks about US and global energy / environmental trends

Ø Definition of Internal Combustion Engines (ICEs)Ø Types of ICEsØ History and evolution of ICEsØ Things you need to know before…Ø What are the alternatives?Ø Practical perspective

Ø (Optional) engine lab tour – 9:15 am tomorrow (Friday) morning, meet at OHE elevators, lab is in OHE basement

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IntroductionØ Hydrocarbon-fueled ICEs are the power plant of choice for

vehicles in the power range from 5 Watts to 100,000,000 Watts, and have been for over 100 years

Ø 200 million ICEs are built every year, ≈ 1.5x the human birth rateØ There is an unlimited amount of inaccurate, misleading and/or

dogmatic information about ICEsØ This seminar's messages

Ø Why ICEs are so ubiquitousØ Why it will be so difficult to replace them with another technologyØ What you will have to do if you want to replace them

Ø Ask questions, challenge me and each other – discussion is more important than lecture

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Topic for discussion

Our current energy economy, based primarily on fossil fuel usage, evolved because it provided the best value (convenience). Is it possible that it's also the most environmentally responsible (or “least environmentally irresponsible”) system?

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US energy usageØ > 80% of world energy production results from combustion of

fossil fuelsØ Energy sector accounts for 9% of US Gross Domestic ProductØ Our continuing habit of burning things and our quest to find more

things to burn has resulted inØ Economic booms and bustsØ Political and military conflictsØ Deification of oil - “the earth’s blood”Ø Global warming (or the need to deny its existence)Ø Human health issues

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Global warmingØ Intergovernmental Panel on Climate Change (> 800 scientists selected

from > 3500 nominations) in 2013 http://www.ipcc.ch/report/ar5/wg1/

“It is extremely likely [>95%] that more than half of the observed increase in global average surface temperature from 1951 to 2010 was caused by the anthropogenic increase in greenhouse gas concentrations and other anthropogenic forcings together”

Currently 405 ppm!

noaa.gov

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Global warming

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US energy flow, 2011, units 1015 BTU/yr

Each 1015 BTU/yr = 33.4 gigawatts

http://www.eia.gov/totalenergy/data/annual/diagram1.cfm

Figure 1.0 Energy Flow, 2011(Quadrillion Btu)

U.S. Energy Information Administration / Annual Energy Review 2011 3

1 Includes lease condensate.2 Natural gas plant liquids.3 Conventional hydroelectric power, biomass, geothermal, solar/photovoltaic, and wind.4 Crude oil and petroleum products. Includes imports into the Strategic Petroleum Reserve.5 Natural gas, coal, coal coke, biofuels, and electricity.6 Adjustments, losses, and unaccounted for.7 Natural gas only; excludes supplemental gaseous fuels.8 Petroleum products, including natural gas plant liquids, and crude oil burned as fuel.

9 Includes 0.01 quadrillion Btu of coal coke net imports.10 Includes 0.13 quadrillion Btu of electricity net imports.11 Total energy consumption, which is the sum of primary energy consumption, electricity retail

sales, and electrical system energy losses. Losses are allocated to the end-use sectors inproportion to each sector’s share of total electricity retail sales. See Note, “Electrical SystemsEnergy Losses,” at end of Section 2.

Notes: • Data are preliminary. • Values are derived from source data prior to rounding forpublication. • Totals may not equal sum of components due to independent rounding.

Sources: Tables 1.1, 1.2, 1.3, 1.4, and 2.1a.

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US energy demand

2.25 gigawatt coal power plant (Page, AZ), 34% coal-to-electricity efficiency

US total energy demand (not just electrical) ≈ 490 of these, running continuously 24/7

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Inflation-adjusted gasoline pricesØ $2.64/gal ± 50% for last 100 yearsØ Even during energy “crises” prices didn’t change that muchØ The public is much more sensitive to the rate of change in price

than the price itself

inflationdata.com

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Classification of ICEsØ Definition of an ICE: a heat engine in which the heat source is a

combustible mixture that also serves as the working fluidØ The working fluid in turn is used either to

Ø Produce shaft work by pushing on a piston or turbine blade that in turn drives a rotating shaft or

Ø Creates a high-momentum fluid used directly for propulsive force

Is an ICEØ Gasoline-fueled reciprocating

piston engineØ Diesel-fueled reciprocating

piston engineØ Gas turbineØ Rocket

Is not an ICEØ Steam power plantØ Solar power plantØ Nuclear power plant

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ICE family tree

TurboshaftAll shaft work to drive propeller,

generator, rotor (helicopter)

TurbofanPart shaft, part jet -"ducted propeller"

TurbojetAll jet except for work needed to

drive compressor

Gas TurbineUses compressor and turbine,

not piston-cylinder

RamjetNo compressor or turbine

Use high Mach no. ram effect for compression

Solid fuelFuel and oxidant are premixed

and put inside combustion chamber

Liquid fuelFuel and oxidant are initially separatedand pumped into combustion chamber

RocketCarries both fuel and oxidantJet power only, no shaft work

Steady

Two-strokeOne complete thermodynamic cycle

per revolution of engine

Four-strokeOne complete thermodynamic cycle

per two revolutions of engine

Premixed-chargeFuel and air are mixed before/during compression

Usually ignited with spark after compression

Two-strokeOne complete thermodynamic cycle

per revolution of engine

Four-strokeOne complete thermodynamic cycle

per two revolutions of engine

Non-premixed chargeOnly air is compressed,

fuel is injected into cylinder after compression

Non-steady

Internal Combustion Engines

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Largest internal combustion engineØ Wartsila-Sulzer RTA96-C turbocharged two-stroke diesel, built in Finland,

used in container shipsØ 14 cyl. version: weight 2300 tons; length 89 feet; height 44 feet; max.

power 108,920 hp @ 102 rpm; max. torque 5,608,312 ft lb @ 102 RPMØ Power/weight = 0.024 hp/lbØ Also one of the most efficient IC engines: 51%

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Most powerful internal combustion engineØ Wartsila-Sulzer RTA96-C is largest IC engine, but Space Shuttle Solid

Rocket Boosters are most powerful (≈ 42 million horsepower (32 hp/lb); not shaft power but kinetic energy of exhaust stream)

Ø Most powerful shaft-power engine: Siemens SGT5-8000H stationary gas turbine (340 MW = 456,000 HP) (0.52 hp/lb) used for electrical power generation (natural gas fuel)

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Smallest internal combustion engine

Ø Cox Tee Dee 010Application: model airplanesWeight: 0.49 oz.Displacement: 0.00997 in3

(0.163 cm3)RPM: 30,000Power: 5 wattsIgnition: Glow plug

Ø Typical fuel: 65% methanol,15% nitromethane, 20% castor oil

Ø Good power/weight (0.22 hp/lb) but poor performanceØ Low efficiency (< 3%)Ø Emissions & noise unacceptable for many applications

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History of automotive enginesØ 1859 - Oil discovered at Drake's

Well, Titusville, Pennsylvania (20 barrels per day) - 40 year supply

Ø 1876 - Premixed-charge 4-stroke engine – Nikolaus OttoØ 1st “practical” ICEØ Overhead valves + crankshaftØ 5.1 liter; 1300 lb; 160 RPM; 2 hpØ Fuel: coal gas (CO + H2)Ø Compression Ratio (CR) = 4 (knock

limited), 14% efficiency (theory 38%)

Ø Today CR = 9 (still knock limited), 30% efficiency (theory 55%)

Ø In 138 years, the main efficiency improvement is due to better fuel

Efficiency= What you getWhat you pay for

= Work outputFuel energy input

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Engine knock - movies

No knock

Videos courtesy Prof. Yuji Ikeda, Kobe University

Knock

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History of automotive enginesØ 1897 - Nonpremixed-charge (Diesel) engine -

compress air only then inject fuel - higher efficiency due toØ Higher CR (no knocking)Ø No throttling loss - use fuel/air ratio to control

powerØ 1901 - Spindletop Dome, east Texas - Lucas

#1 gusher produces 100,000 barrels per day -ensures that “2nd Industrial Revolution” will be fueled by oil, not coal or wood - 40 year supply

Ø 1921 - Tetraethyl lead anti-knock additive discovered at General MotorsØ Enabled higher CR (thus more power, better

efficiency) in Otto-type enginesØ “End of the line” for steam

& electric vehicles

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History of automotive enginesØ 1938 – Oil discovered at Dammam, Saudi Arabia (40 year

supply)Ø 1952 - A. J. Haagen-Smit, Caltech

NO + UHC + O2 + sunlight ® NO2 + O3(from exhaust) (brown) (irritating)

(UHC = unburned hydrocarbons)

Ø 1960s - Emissions regulationsØ Detroit wouldn’t believe itØ Initial stop-gap measures - lean mixture, exhaust gas recirculation

(EGR), retard sparkØ Poor performance & fuel economy

Ø 1973 & 1979 - The energy crises due to Middle East turmoilØ Detroit takes a bath, Asian and European imports increase

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History of automotive enginesØ 1975 - Catalytic converters, unleaded fuel

Ø More “aromatics” (e.g., benzene) in gasoline - high octane but carcinogenic, soot-producing

Ø 1980s - Microcomputer control of enginesØ Tailor operation for best emissions, efficiency, ...

Ø 1990s - Reformulated gasoline (e.g., MTBE)Ø Reduced need for aromatics, cleaner (?)Ø ... but higher cost, lower miles per gallonØ Then we found that MTBE pollutes groundwater!!!Ø Alternative “oxygenated” fuel additive - ethanol - very attractive to

powerful senators from farm states in the USA

MTBE Ethanol

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History of automotive enginesØ 2000s - hybrid vehicles

Ø Use small gasoline engine operating at maximum power (most efficient way to operate) or turned off if not needed

Ø Use generator/batteries/motors to make/store/use surplus power from gasoline engine

Ø Plug-in hybrid: half-way between conventional hybrid and electric vehicle

Ø 2 benefits to car manufacturers: win-win» Consumers pay a premium for hybrids» Helps to meet fleet-average standards for efficiency & emissions

Ø Do fuel savings justify extra cost? Consumer Reports study: only 1 of 7 hybrids tested showed a cost benefit over a 5 year ownership if tax incentives were removed» Dolly Parton: “It costs a lot of money to look this cheap”» PDR: “You have to consume a lot of energy to save a little fuel”

Ø 2010 and beyondØ Electric vehiclesØ Small turbocharged gasoline engines (e.g. Ford EcoBoost™)

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Things you need to understand before ...

…you invent the zero-emission, 100 mpg 1000 hp engine, revolutionize the automotive industry and shop for your retirement home on the French Riviera

Ø Room for improvement - factor of less than 2 in efficiencyØ Ideal Otto cycle engine with compression ratio = 9: 55%Ø Real engine: ≤ 30%Ø Differences because of

» Throttling losses » Heat losses» Friction losses» Slow burning» Incomplete combustion is a very minor effect

Ø Majority of power is used to overcome air resistance - smaller, more aerodynamic vehicles beneficial

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Things you need to understand before ...

Ø Room for improvement - infinite in pollutantsØ Pollutants are a non-equilibrium effect

» Burn: Fuel + O2 + N2 ® H2O + CO2 + N2 + CO + UHC + NOOK OK(?) OK Bad Bad Bad

» Expand: CO + UHC + NO “frozen” at high levels» With slow expansion, no heat loss:

CO + UHC + NO ® H2O + CO2 + N2

...but how to slow the expansion and eliminate heat loss?Ø Worst problems: cold start, transients, old or out-of-tune

vehicles - 90% of pollution generated by 10% of vehicles

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Things you need to understand before ...Ø Room for improvement - very little in power

Ø IC engines are air processors» Fuel takes up little space» Air flow = power» Limitation on air flow due to

• “Choked” flow past intake valves• Friction loss, mechanical strength - limits RPM• Slow burn

» How to increase air flow?• Larger engines• Faster-rotating engines • Turbocharge / supercharge

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Alternative #1 - external combustionØ Examples: steam engine, Stirling cycle engine

Ø Use any fuel as the heat sourceØ Use any working fluid (high g, e.g. helium, provides better efficiency)

Ø Heat transfer rateØ Heat transfer per unit area (q/A) = k(dT/dx)Ø Turbulent mixture inside engine: k ≈ 100 kno turbulence ≈ 2.5 W/mKØ dT/dx ≈ DT/Dx ≈ 1500K / 0.02 mØ q/A ≈ 187,500 W/m2

Ø Combustion: q/A = rYfQRST = (10 kg/m3) x 0.067 x (4.5 x 107 J/kg) x 2 m/s = 60,300,000 W/m2 - 321x higher!

Ø CONCLUSION: HEAT TRANSFER IS TOO SLOW!!!Ø That's why 10 large gas turbine engines ≈ large (1 gigawatt) coal-

fueled electric power plant

k = gas thermal conductivity, T = temperature, x = distance,r = density, Yf = fuel mass fraction, QR = fuel heating value, ST = turbulent flame speed in engine

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Alternative #2 - electric vehicles (EVs)

Ø Generate electricity in central power plant (efficiency h ≈ 35%), charge batteries, run electric motors (h ≈ 90%)

Ø Chevy Bolt Li-ion battery Ø 60 kWh (100% - 0% charge, diminishes battery life), 960 pounds =

5.0 x 105 J/kg (http://en.wikipedia.org/wiki/Chevrolet_Bolt)Ø Replacement list price $15,700

Ø Gasoline (and other hydrocarbons): 4.3 x 107 J/kgØ Even at 30% efficiency (gasoline) vs. 90% (batteries), gasoline

has 29 times higher energy/weight than batteries! Ø 1 gallon of gasoline ≈ 175 pounds of batteries for same energy

delivered to the wheelsØ Also – recharging rate: 7 KW (EV, home) or 85 KW (Tesla

Supercharger station) vs. 5000 KW (gasoline pump)

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“Zero emission” electric vehicles

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Alternative #2 - electric vehicles (EVs)Ø Other issues with electric vehicles

Ø "Zero emissions” ??? - EVs export pollutionØ MPGe = “equivalent” energy based only on electrical energy stored in

the battery, not the energy required to generate that electricity» 100 MPGe ≈ 35 MPG in terms of fuel burned (and CO2 produced)

Ø 33% of US electricity is by produced via coal at 35% efficiency –virtually no reduction in CO2 emissions with EVs

Ø Environmental cost of battery materialsØ Possible advantage: makes smaller, lighter, more streamlined cars

acceptable to consumersØ Plus side: cost of electricity (Joules/$) ≈ same as gasoline but ≈ 3x

higher efficiency (fuel to shaft power), thus EVs have lower “fuel” costØ Economics of batteries

Ø Bulk Li-ion batteries cost ≈ $500/kW-hr (GM supplier: $145/kW-hr)Ø Lifetime 1000 charge/discharge cycles, thus $0.50/kW-hrØ Cost of electricity ≈ $0.10/kW-hr Ø Battery cost is 5x greater than value of all electricity it can store over

its entire lifetime – Tesla Powerwall™ makes no financial sense without subsidies

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Alternative #2 - electric vehicles (EVs)Ø Tesla

Ø Different strategy - performance car, not economy car – excels in acceleration, handling, …

Ø “Zero Emission Vehicle” credits – worth ≈ $35,000 per vehicle (LA Times, 8/23/2013, page B4)

Ø Cost ≥ $81,000 with 85 kW-hr battery (1200 lb) (5.6 x 105 J/kg)Ø “Free” electricity at their charging stations – what is value?

Ø Option to replace battery after 8 years: $12,000 – more than wipes out free recharges

100,000 miles× gallon35 miles

×$2.50gallon

= $7,143

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Ø NuCellSys HY-80 “Fuel cell engine”(power/wt = 0.19 hp/lb)

Ø 48% efficient (fuel to electricity)Ø MUST use hydrogen (from where?

H2 is an energy carrier, not a fuel)Ø Requires > $10,000 of platinum Ø Does NOT include electric drive systemØ Overall system: 0.13 hp/lb at 43% efficiencyØ Conventional engine: ≈ 0.5 hp/lb at 30% efficiency Ø Conclusion: fuel cell engines only marginally more efficient, much

heavier & require hydrogen vs. gasolineØ Prediction: even if we had an unlimited free source of hydrogen

and a perfect way of storing it on a vehicle, we would still burn it, not use it in a fuel cell

Alternative #3 - Hydrogen fuel cell

nucellsys.com

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Hydrogen storageØ Hydrogen is a great fuel

Ø High energy density (1.2 x 108 J/kg, ≈ 3x hydrocarbons)Ø Faster reaction rates than hydrocarbons (≈ 10 - 100x at same T)Ø Excellent electrochemical properties in fuel cells

Ø But how to store it???Ø Cryogenic (very cold, -424˚F) liquid, low density (14x lower than water)Ø Compressed gas: weight of tank ≈ 15x greater than weight of fuelØ Borohydride solutions

» NaBH4 + 2H2O ® NaBO2 (Borax) + 3H2» (mass solution)/(mass fuel) ≈ 9.25

Ø Palladium - Pd/H = 164 by weightØ Carbon nanotubes - many claims, few facts…Ø Long-chain hydrocarbon (CH2)x: (Mass C)/(mass H) = 6, plus C atoms

add 94.1 kcal of energy release to 57.8 for H2!Ø MORAL: By far the best way to store hydrogen is to attach it to

carbon atoms and make hydrocarbons, even if you're not going to use the carbon as fuel!

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Alternative #4 - solar vehiclesØ Arizona, high noon, mid summer: solar flux ≈ 1000 W/m2

Ø Gasoline engine, thermal power = (60 mi/hr / 30 mi/gal) x (6 lb/gal) x (kg / 2.2 lb) x (4.3 x 107 J/kg) x (hr / 3600 sec) = 65 kilowatts

Ø Need ≈ 65 m2 collector ≈ 26 ft x 26 ft - lots of air drag, what about underpasses, nighttime, bad weather, northern/southern latitudes, etc.?

Do you want to drive one of these every day (but never at night?)

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Alternative #4 - solarØ Ivanpah solar thermal electric generating station (California desert)

Ø 3 towers, each 460 ft tall; land area 6 mi2, 173,500 mirrors Ø 400 MW maximum power, 203 MW annual average in 2016 (typical coal or

nuclear plant: 1,000 MW)Ø Annual natural gas usage (to keep boilers hot at night): 111 MWØ Capital cost $2.2 billion = $18/watt vs. $1/watt for natural gas power plants,

$3/watt for coal … and maintenance costs?Ø Impact on desert wildlife? (28,000 birds/yr?)

Ø Topaz solar photovoltaic, near Bakersfield: 144 MW avg., $17/watt

AME 436 - Spring 2016 - Lecture 1 - Introduction

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Alternative #5 - biofuelsØ Essentially solar energy – “free” (?)Ø Barely energy-positive; requires energy for planting, fertilizing,

harvesting, fermenting, distillingØ Very land-inefficient compared to other forms of solar energy – life

forms convert < 1% of sun’s energy into combustible materialØ Until 2011, 3 subsidies on US bio-ethanol:

Ø 45¢/gal (≈ 67¢/gal gasoline) tax credit to refiners

Ø 54¢/gal tariff on sugar-based ethanol imports

Ø Requirement for 10% ethanol in gasoline

Ø Displaces other plants – not necessarily “carbon neutral”

Ø Uses other resources - arable land, water – that might otherwise be used to grow foodor provide biodiversity (e.g. in tropical rain forests)

AME 436 - Spring 2016 - Lecture 1 - Introduction

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Alternative #6 - nuclearØ Who are we kidding ???Ø High energy density though

Ø U235 fission: 8.2 x 1013 J/kg ≈ 2 million x hydrocarbons!Ø Radioactive decay much less (2.0 x 109 J/kg for Pu-238), but still

much higher than hydrocarbons

Ford Nucleon concept car (1958)

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Alternative #7 – common senseØ http://www.edison2.comØ Won X-prize competition for 4-passenger vehicles (110 MPG)Ø Low weight (830 lb), aerodynamic, very low rolling resistanceØ Engine: 1 cylinder, 40 hp, 250 cc, turbocharged ICEØ Ethanol fuel (high octane, allows high CR thus high efficiency)Ø Rear engine placement reduces air drag due to radiatorØ Beat electric vehicles despite unfair advantage in US EPA MPG

equivalency: 33.7 kW-hr electrical energy = 1 gal, same as raw energy content of gasoline – doesn’t account for fuel burned to create electrical energy!

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Ø Total “cradle to grave” CO2 emissions ≈ same for all propulsion methods and energy sources!

Conclusion - alternatives to IC engines

http://www.hydrogen.energy.gov/pdfs/14006_cradle_to_grave_analysis.pdf

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Summary of advantages of ICEsØ Moral - hard to beat liquid-fueled internal combustion engines for

Ø Power/weight & power/volume of engineØ Energy/weight (4.3 x 107 J/kg) & energy/volume of liquid

hydrocarbon fuelØ Distribution & handling convenience of liquids Ø Relative safety of hydrocarbons compared to hydrogen or nuclear

energyØ Cost of materials (steel & aluminum)

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Practical alternatives…Ø Conservation!Ø Combined cycles

Ø Use hot exhaust from ICE to heat water for conventional steam cycleØ Can achieve > 60% efficiencyØ Not practical for vehicles - too much added volume & weight

Ø Natural gas (NG) – mostly methane (CH4)Ø 4x cheaper than electricity, 2x cheaper than gasoline or diesel for

same energyØ Somewhat cleaner than gasoline or diesel, but no environmental

silver bulletØ Low energy storage density - 4x lower than gasoline or dieselØ Lowest CO2 emissions of any fossil fuel sourceØ Problem: greenhouse effect of unburned NG (from production wells,

filling stations, etc.) ≈ 8x that of burned NG

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Practical alternatives… discussion pointsØ Fischer-Tropsch fuels - liquid hydrocarbons from coal or natural gas

Ø Coal or NG + O2 à CO + H2 à liquid fuelØ Competitive with $75/barrel oilØ Cleaner than gasoline or dieselØ … but using coal increases greenhouse gases!

Coal : oil : natural gas = 2 : 1.5 : 1Ø What about using biomass (e.g. agricultural waste) instead of coal or

natural gas as “energy feedstock” Ø But really, there is no way to decide what the next step is until it is

decided whether there will be a tax on CO2 (and maybe other greenhouse gas) emissions

Ø Personal opinion: most important problems are (in order of priority)Ø Global warmingØ Energy independenceØ Environment

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ConclusionsØ IC engines are the worst form of vehicle propulsion, except for all

the other formsØ Oil costs too much, but it's still very cheapØ We're 40 years away from running out of oil, and have been for

the past 150 yearsØ There is no constituency for holistic, cradle-to-grave view of

energy production with least total environmental impact